Relating cultivar resistance to sugarcane yield using breeding selection trial analyses; orange rust and yellow spot

摘要

Plant breeders in the Australian sugar industry conduct yield assessment trials each year to assess the yielding ability of clones in the sugarcane breeding programme. Several endemic diseases impinge on the yield of these clones and the tested clones vary greatly in disease susceptibility. In this study, resistance to the diseases orange rust and yellow spot was assessed in final stage trials in the Northern Queensland programme. Clonal yielding ability was related to disease resistance. The results indicate that both diseases, but particularly yellow spot, influenced the yield (tonnes cane/ha and tonnes sugar/ha) of clones in northern breeding trials in 2000. Yield loss estimates were calculated, as well as the relationship between resistance and yield. There was a high level of resistance to orange rust in clones in these trials but much less resistance to yellow spot; the resistance index or orange rust was 2.2 while for yellow spot it was 5.5. Yield loss resistance index values of 5.0 and above for orange rust suggest there is adequate resistance in clones to minimise losses from this disease. In contrast, the yield loss resistance index for yellow spot (tonnes cane/ha) was below 5.0, therefore, it is concluded that during the 2000 harvest season, there was inadequate resistance to minimise losses. The information gathered from this research will be used to determine the level of leaf disease resistance needed in commercial cultivars to optimise yielding ability. Such decisions should improve the efficiency of selection and the performance of commercial cultivars in the Australian sugar industry.